1. Field of Invention
The present invention relates to systems, devices, programs, and methods for performing differential communication, and more particularly to a differential communication system, a differential communication device, a differential communication program, and a differential communication method, which are preferable for performing differential communication in a dynamically configured network.
2. Description of Related Art
During communication between a transmitting device and a receiving device, what is called “differential communication” can be used to reduce the amount of communication and to improve confidentiality. In this differential communication, the transmission device and the receiving device hold common reference information in communication therebetween, such that the transmission device transmits difference information, which is a difference between plain information and the reference information, to the receiving device, which in turn restores the original plain information from the received difference information and the reference information.
Conventionally, for example, available technologies for differential communication include a remote maintenance system (hereinafter referred to as a “first conventional example”) disclosed in Japanese Unexamined Patent Application Publication No. H7-175662, a partial-extraction-type remote maintenance system (hereinafter referred to as a “second conventional example”) disclosed in Japanese Unexamined Patent Application publication No. H11-265309, and a financial transaction processing system (hereinafter referred to as a “third conventional example”) disclosed in Japanese Unexamined Patent Application Publication No. 2000-048106.
In the first conventional example, a host computer and a remote computer are connected over a network. At the host computer, first, a change-history generating section generates a change history for an old source program in a storage device, the old source program being designated by a remote computer. A modification-program storage section stores a change history containing modified-line information. An edit-information generating section generates edited information for each communication. A transmitting section transmits the edited information for each communication to the remote computer. At the remote computer, first, a receiving section receives the edited information for each communication and composes a change history for an old source program in a storage device. A program updating section generates a new source program from the change history and the old source program. A compiling section compiles the new source program to generate a new execution-format program.
This arrangement can minimize the amount of data transmitted, and can facilitate a program update for a remote computer without affecting the system operation.
In the second conventional example, a host computer and a remote computer are connected over a network. The host computer includes a difference-information extracting section, a verification-code generating section, and a distributing section. When data stored in the host computer is changed, the difference-information extracting section compares the contents of the data before it is changed and the contents thereof after it is changed, to extract difference information therefor. The verification-code generating section generates a verification code concerning the changed contents. The distributing section distributes change information, which contains the difference information, and the verification code to the remote computer. The remote computer updates the contents of data stored in its own terminal, in accordance with the change information, and generates a verification code from the updated contents. The remote computer also includes a verification-code checking section for checking the generated verification code against a verification code that is transmitted from the host computer.
Thus, upon update of data at the host computer, the amount of data transmitted for updating data in the remote computer can be reduced and the contents of the updated data can be verified at the remote computer.
In the third conventional example, a payment server and a client are connected over a network. The client transmits the date and time of update of a financial-organization-name table and the date and time of update of a branch-name table to the payment server. In response to the transmitted contents, the payment server transmits difference data to the client, which, in turn, uses the difference data to update the financial-organization-name table and the branch-name table and also transmits the updated contents to the payment server.
Thus, in bank transaction utilizing a network, all the names of financial organizations and branches with which transaction is possible can be selected at the time of a transaction, and transaction-processing time can be reduced by minimizing the amount of data communicated during a transaction.